18.1. Biodiversity

Question 1

Species

Answer 1

a group of organisms with similar morphology and physiology, which can breed together to produce fertile offspring and are reproductively isolated from other species

Question 2

Problems of the definition of Species

Answer 2

• Asexual reproduction? - no breeding
• Genetic Sequencing?
• Dogs with dissimilar morphology can reproduce - Chihuahua and Great Dane

Question 3

Ecosystem

Answer 3

a relatively self-contained, interacting community of organisms, and the environment in which they live and with which they interact.

• A self-sustaining unit consisting of abiotic and biotic factors interacting together
• Includes all organisms of all populations (in a given area)
• Energy flows through and cycling of minerals occur

Question 4

Examples of Ecosystem

Answer 4

• Tropical Rainforests
• Rivers
• Coral reefs
• Woodland
• Sandy desert

Question 5

Niche

Answer 5

The role of an organism in the ecosystem. It includes where it lives and how it obtains its energy

Question 6

Biodiversity

Answer 6

Degree of variation of lifeforms in an ecosystem

Question 7

Biodiversity is made up of:

Answer 7

1) The number of species and their relative abundance
2) Genetic variation within each species
3) Variation in ecosystem or habitats

Question 8

Species Diversity

Answer 8

• The variety of species within a habitat or a region, and the abundance of the different species
• Some habitats, such as rainforests and coral reefs, have many species. Others, such as salt flats or a polluted stream, have fewer

Question 9

Genetic Diversity

Answer 9

• The variety of alleles within a species
• Each species is made up of individuals that have their own particular genetic composition.
• This means a species may have different populations, each having different genetic compositions

Question 10

Variation in ecosystems or habitats

Answer 10

• Ecosystem diversity is the variety of ecosystems in given place
• An ecosystem is a community of organisms and their physical environment interacting together
• An ecosystem can cover a large area, such as a whole forest, or a small area, such as a pond

Question 11

Abiotic Factors

Answer 11

non-living chemical and physical factors in the environment which affect ecosystems

Question 12

Biotic Factors

Answer 12

a living component of an ecosystem; for example organisms, such as plants and animals

Question 13

Stratified Sampling

Answer 13

• Stratified sampling is simply the process of identifying areas within an overall habitat, which may be very different from each other and which need to be sampled separately.
• Each individual area separately sampled within the overall habitat is then called a stratum.
• The habitat may be fairly uniform, in which case, this is unnecessary
• Within stratified sampling, there is random sampling and systematic sampling

Question 14

Random Sampling

Answer 14

Used when an area looks reasonably uniform, or if there is no clear pattern to the way species are distribute

• like by using a random number generator
• the random numbers give you the coordinates of the sampling points in relation to the two tapes you have used to mark out the area

Question 15

Quadrat

Answer 15

a square frame that marks off an area of ground, or water, where you can identify the different species present and/or take a measurement of their abundance
- no use for counting animals

Question 16

Why take random samples?

Answer 16

• To remove observer bias in the selection of samples.
• Where statistical tests are to be used which require randomly collected data.
• Where a large area needs to be covered quickly.
• If time is very limited.

Question 17

Using a frame quadrat to estimate species frequency

Answer 17

a measure of the chance of a particular species being found within any one quadrat

• you simply record whether the species was present in each quadrat that you analyse
• like out of 50 times you see the same species 22 times so the species frequency is 22/50 = 44%

Question 18

Using a frame quadrat to estimate percentage cover species density

Answer 18

a measure of how many individuals there are per unit area – for example, per square metre.
- The number of individuals that you have counted is divided by the total area of all your quadrats

Question 19

Using a frame quadrat to estimate percentage cover

Answer 19

• not always possible to count individual plants and animals because of the way that they grow
• sometimes it is impossible to count individuals
• you can use a 100 cm × 100 cm quadrat with wires running across it at 10 cm intervals in each direction, dividing the quadrat into 100 smaller squares.
• you then decide approximately what percentage of the area inside the quadrat is occupied by each species

Question 20

Estimating number of mobile animals

Answer 20

Small mammals, such as mice and voles, can be caught in traps that are filled with hay for bedding and suitable food as bait

• The techniques for this vary according to the size of the body of water, and whether it is still or moving
• Method –> mark-release-recapture technique

Question 21

Mark–release–recapture technique

Answer 21

1) As many individuals as possible are caught. Each individual is marked, in a way that will not affect its future chance of survival
2) The marked individuals are counted, returned to their habitat and left to mix randomly with the rest of the population
3) When enough time has elapsed for the mixing to take place, another large sample is captured.
4) The number of marked and unmarked individuals is counted.
5) The proportion of marked to unmarked individuals is then used to calculate an estimate of the total number in the population

Question 22

Estimating population in the Mark–release–recapture technique

Answer 22

• Estimate population by multplying number caught and marked in 1st sample with number caught in 2nd sample.
• Then divide the whole thing by the number in the second sample that had been marked

Question 23

Simpson’s Index of Diversity

Answer 23

used to calculate a value for the species diversity in that area, once information is collected

D = 1 − ∑ ( ( n / N ) ^2 )

• n is the total number of organisms of a particular species
• N is the total number of organisms of all species

Question 24

Simpson’s Index of Diversity values

Answer 24

• Values of D range from 0 to 1.
• A value near 0 represents a very low species diversity. - A value near 1 represents a very high species diversity
• diversity depends on the number of different species there are, and also the abundance of each of those species

Question 25

Advantage of using Simpson’s Index of Diversity

Answer 25

you do not need to identify all, or even any, of the organisms present to the level of species
- you can just create names for the organisms from their phenotypes

Question 26

Systematic Sampling

Answer 26

To show zonation of species along some environmental gradient. e.g. down a sea shore, across a woodland edge

• area where the physical conditions, such as altitude, soil moisture content, soil type, soil pH, exposure or light intensity change
• used to detect changes in community composition along a line across one or more habitats.

Question 27

Line Transect

Answer 27

• In this case, you should randomly select a starting point in the field and lay out a measuring tape in a straight line to the marshy area.
• You then sample the organisms that are present along the line
• The simplest way to do this is to record the identity of the organisms that touch the line at set set distances – for example, every two metres.
• This line transect will give you qualitative data
• The organisms found at regular points along a line are noted.

Question 28

Belt Transect

Answer 28

• placing a quadrat at regular intervals along the line and recording the abundance of each species within the quadrat.
• the abundance of organisms within quadrats placed at regular points along a line is noted.
• data from a line transect can be shown as a drawing.
• data from a belt transect can be plotted as a set of bar charts or as a kite diagram

Question 29

Correlation

Answer 29

plot on scatter graph to make it easier to identify correlation

3 types

1) positive linear correlation
2) no correlation
3) negative linear correlation.

Question 30

When would you use Pearson’s correlation coefficient?

Answer 30

• can only be used where you can see that there might be a linear correlation
• when you have collected quantitative data as measurements (for example, length, height, depth, light intensity, mass) or counts (for example, number of plant species in quadrats).
• data must be distributed normally, or you must be fairly sure that this is the case.

Question 31

When would you use Spearman’s rank correlation?

Answer 31

• if you used an abundance scale
• If you may not be sure if your quantitative data is normally distributed.
• It might also be possible that a graph of your results shows that the data is correlated, but not in a linear fashion

Question 32

Correlation vs Relationship

Answer 32

• Remember that correlation does not mean that changes in one variable cause changes in the other variable.
• These correlation coefficients are ways for you to test a relationship that you have observed and recorded to see if the variables are correlated and, if so, to find the strength of that correlatio

Question 33

Spearman’s rank correlation

Answer 33

involves ranking the data recorded for each variable and assessing the difference between the ranks

rs = 1 − ( (6 * ∑D^2) / n^3 - n) )

• where n is the number of pairs of items in the sample
• D is the difference between each pair of ranked measurements and ∑ is the ‘sum of’

Question 34

Pearson’s linear correlation

Answer 34

used the data collected are for two continuous variables and the data within each variable show a normal distribution

r = (∑xy − (n * mean x * mean y) ) / (n * sx * sy)